Zotac says that wake-on-USB isn't currently supported by the PCB and requires a hardware revision to enable it. A new revision of the Zotac Ion board with wake-on-USB support is in the works and Zotac tells me that the new board should be ready in early June.

Zotac also tells me that the Ion user manual should be the first place to look to see if your version of the board supports wake-on-USB. Given that none of the boards support it currently, don't expect to see any reference to the feature in the current version of the manual :)

As always, I'll keep you posted. But for now, back to testing some new CPUs :)